Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A plasma device includes: a reaction chamber; an upper electrode
positioned upward in the reaction chamber; a lower electrode facing the
upper electrode; a baffle plate enclosing the lower electrode and
including a plurality of cutouts formed at the edge thereof, wherein a
boundary line of the cutout is connected to a boundary line of the baffle
plate, thereby forming a recess portion at the edge of the baffle plate.
The cutouts of the baffle plate change the flow of the reactive gas in
the chamber, helping achieve a more uniform etch.

Claims:

1. A plasma device comprising: a reaction chamber; an upper electrode
positioned in the reaction chamber; a lower electrode facing the upper
electrode; and a baffle plate enclosing the lower electrode and including
an edge having a plurality of cutouts, forming a recess portion at the
edge of the baffle plate.

2. The plasma device of claim 1, further comprising a focusing ring
positioned on the lower electrode, wherein the cutout is spaced from an
imaginary extension line extending from an edge of the focusing ring by
1.3 times to 1.9 times the diameter of the cutout.

3. The plasma device of claim 2, wherein the size of the cutout is 1/18
times to 1/23 times a long axis length of the baffle plate.

4. The plasma device of claim 1, wherein the baffle plate is
quadrangular.

5. The plasma device of claim 1, wherein the cutout has as semi-circular
cross section.

6. The plasma device of claim 1, wherein each cutout includes a plurality
of slits.

7. The plasma device of claim 1, wherein the size of the cutout is in the
range of 1/18 times to 1/23 times the long side of the baffle plate.

8. The plasma device of claim 1, wherein the lower electrode comprises a
substrate elevator and an electrostatic chuck configured to support a
substrate.

9. The plasma device of claim 1, wherein a ratio of a corner area: a
cutout area is between 100:0 and 100:18.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and the benefit of Korean
Patent Application No. 10-2011-0043511 filed in the Korean Intellectual
Property Office on May 9, 2011, the entire contents of which are
incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] (a) Field of the Invention

[0003] The present invention relates to a plasma device.

[0004] (b) Description of the Related Art

[0005] A thin film transistor (TFT) is used in various fields, and is
particularly used as switching and driving elements in a flat panel
display such as a liquid crystal display (LCD), an organic light emitting
device (OLED) display, and an electrophoretic display.

[0006] A thin film transistor includes a gate electrode connected to a
gate line transmitting a scanning signal, a source electrode connected to
a data line transmitting a signal applied to a pixel electrode, a drain
electrode facing the source electrode, and a semiconductor electrically
connected to the source electrode and the drain electrode.

[0007] The wires and electrodes that connect a thin film transistor to
other components are formed by depositing a thin film on a substrate and
patterning a desired shape through an etching process. The etching method
may be wet etching or dry etching. Dry etching generally uses plasma.

[0008] A plasma processing device includes a reaction chamber, an upper
electrode and a lower electrode facing each other in the reaction
chamber, a high frequency power source applying power to the upper and
lower electrodes to generate plasma, and a baffle plate uniformly
distributing the plasma generated in the reaction chamber and letting the
reaction residue flow toward the exit.

[0009] A reaction gas supplied to the reaction chamber is changed to a
plasma state by using the high frequency power that is applied to the
upper and lower electrodes through a high frequency power source. The
reaction gas, once converted to plasma state, etches a surface of an LCD
panel (hereinafter referred to as "a substrate"). Here, when moving the
lower electrode upward to execute the etching process, a baffle plate
uniformly exhausts a non-reaction gas and a polymer inside the reaction
chamber to a lower side of the reaction chamber.

[0010] The baffle plate provided is fixed to the inner wall of the chamber
under a gate door where the substrate is input and output, causing the
plasma formed inside the reaction chamber to leak to the outside of the
lower electrode. Particularly, the plasma becomes more concentrated
around the gate door when the lower electrode loaded with the substrate
is moved upward to execute the plasma process and the plasma is formed
between the upper electrode and the lower electrode.

[0011] The plasma in the chamber is non-uniformly distributed due to this
phenomenon such that the edge of the substrate becomes over-etched, and
this is represented as a spot of the liquid crystal display.

[0012] The above information disclosed in this Background section is only
for enhancement of understanding of the background of the invention and
therefore it may contain information that does not form the prior art
that is already known in this country to a person of ordinary skill in
the art.

SUMMARY OF THE INVENTION

[0013] A plasma device that uniformly etches a substrate is presented.

[0014] In one aspect, the invention is a plasma device that includes: a
reaction chamber; an upper electrode positioned in the reaction chamber;
a lower electrode facing the upper electrode; and a baffle plate
enclosing the lower electrode and including an edge having a plurality of
cutouts forming a recess portion at the edge of the baffle plate.

[0015] A focusing ring may be positioned on the lower electrode, wherein
the cutout is spaced from an imaginary extension line extending from an
edge of the focusing ring by 1.3 times to 1.9 times the diameter of the
cutout.

[0016] The size of the cutout may be 1/18 times to 1/23 times a long axis
length of the baffle plate.

[0017] The baffle plate may be quadrangular.

[0018] The cutout may have a semi-circular cross section.

[0019] Each cutout may include a plurality of slits.

[0020] The lower electrode may include a substrate elevator and an
electrostatic chuck configured to support a substrate.

[0021] A ratio of the baffle plate area to a cutout area is between 100:18
and 100:0.

[0022] According to an exemplary embodiment of the present invention, the
substrate is uniformly etched in the plasma device such that the display
quality of the liquid crystal display may be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The patent or application file contains at least one drawing
executed in color. Copies of this patent or patent application
publication with color drawings will be provided by the U.S. Patent and
Trademark Office upon request and payment of the necessary fee.

[0024] FIG. 1 is a schematic cross-sectional view of a plasma device
including a baffle plate according to an exemplary embodiment of the
present invention.

[0025] FIG. 2 is a perspective view of a lower electrode part of a plasma
device including a baffle plate according to the present invention.

[0026] FIG. 3 is a top plan view of a cutout according to another
exemplary embodiment of the present invention.

[0027] FIG. 4 is a view of a simulation of turbulence energy when using a
baffle plate according to an exemplary embodiment of the present
invention.

[0028] FIG. 5 is a view of a simulation of surface stress when using a
baffle plate according to an exemplary embodiment of the present
invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The present invention will be described more fully hereinafter with
reference to the accompanying drawings, in which exemplary embodiments of
the invention are shown. As those skilled in the art would realize, the
described embodiments may be modified in various ways without departing
from the spirit or scope of the present invention.

[0030] In the drawings, the thickness of layers, films, panels, regions,
etc., are exaggerated for clarity. Like reference numerals designate like
elements throughout the specification. It will be understood that when an
element such as a layer, film, region, or substrate is referred to as
being "on" another element, it can be directly on the other element or
intervening elements may also be present. In contrast, when an element is
referred to as being "directly on" another element, there are no
intervening elements present.

[0031] Thus, a plasma device according to an exemplary embodiment of the
present invention will be described with reference to FIG. 1 to FIG. 3.

[0032] FIG. 1 is a schematic cross-sectional view of a plasma device
including a baffle plate according to an exemplary embodiment of the
present invention, FIG. 2 is a perspective view of a lower electrode part
of a plasma device including a baffle plate according to the present
invention, and FIG. 3 is a top plan view of a cutout according to another
exemplary embodiment of the present invention.

[0033] Referring to FIG. 1, a plasma device of the present invention
includes a reaction chamber 100, an upper electrode part 200 and a lower
electrode part 300 facing each other in the reaction chamber 100, and a
baffle plate 400. The lower electrode part 300 includes a substrate
elevator 320 and an electrostatic chuck 340. The baffle plate 400 fits
around the electrostatic chuck 340.

[0034] The reaction chamber 100 provides a closed and sealed space while
an etching process is executed. A gate door 110 to load and unload a
substrate G is formed at one side of the reaction chamber 100. In FIG. 1,
one gate door 110 is formed at one side of the reaction chamber 100.
However, this is not a limitation of the invention, and the gate door 110
may be formed at both sides, thereby separately executing loading and
unloading.

[0035] The reaction chamber 100 is connected to an exhaust means through
which gas inside the reaction chamber 100 exit the chamber 100 during the
etching process. The exhaust means includes an exhaust port 120 and an
exhaust device 130.

[0036] The upper electrode part 200 includes an insulating supporting
member 220 positioned in the reaction chamber 100 and an upper electrode
plate 240 coupled to a lower surface of the insulating supporting member
220. The insulating supporting member 220 is formed with an inner space
260 that is empty, and a plurality of gas discharge holes 280a that are
formed under the inner space 260.

[0037] The upper electrode plate 240 is made of aluminum and includes gas
discharge holes 280b connected to the gas discharge holes 280a formed at
the insulating supporting member 220 and extending through the upper
electrode plate 240.

[0038] A gas supplying unit 500 and an upper high frequency power source
part 600 to generate the plasma are connected to the upper electrode part
200.

[0039] The gas supplying unit 500 includes a gas supplying source (not
shown) and a mass flow controller (MFC, not shown) such that the gas
supplied from the gas supplying source is supplied to the inner space 260
formed at the upper electrode part 200 by controlling the desired amount
by the MFC. Also, the upper high frequency power source unit 600 includes
an upper high frequency power source (not shown) and an upper equalizer
(not shown) such that substantially the same power level that is supplied
from the high frequency power source is supplied to the upper electrode
plate 240.

[0040] Accordingly, if the gas and the high frequency power are supplied
and applied to the upper electrode part 200, the gas that is input to the
upper electrode part 200 sprays out through the gas discharge holes 280.
As shown in FIG. 1, the gas discharge holes 280 extend vertically through
the insulating supporting member 220 and the upper electrode plate 240
through the inner space 260 formed in the insulating supporting member
220. The plasma is formed between the upper electrode part 200 and the
lower electrode part 300.

[0041] A sealed ring (not shown) may be further provided to fit around the
side surfaces of the upper electrode part 200. The sealed ring would
prevent abnormal discharge that may be generated in the upper electrode
part 200, and is formed to fit around the side surfaces of the upper
electrode plate 240 and the insulating supporting member 220. Due to the
presence of the upper electrode plate 240, the lower surface of the upper
electrode plate 240 is not exposed.

[0042] Meanwhile, the lower electrode part 300 includes the substrate
elevator 320 separated from the upper electrode part 200 by a
predetermined distance and the electrostatic chuck 340 formed on the
substrate elevator 320. Here, the substrate elevator 320 is connected to
a lower high frequency power source part 700, and the electrostatic chuck
340 is connected to a high voltage DC power source 800.

[0043] The substrate elevator 320 supports the electrostatic chuck 340,
and a lift means 360 is connected under the substrate elevator 320 to
move the electrostatic chuck 340 up and down. Also, a lower electrode
plate (not shown) is formed inside the substrate elevator 320, and the
lower electrode plate is connected to the lower high frequency power
source part 700. The high frequency power source part 700 includes a
lower high frequency power source (not shown) and a lower matcher (not
shown), and a function thereof is the same as that of the upper high
frequency power source part 600. Here, a cooling member (not shown) to
control the temperature of the lower electrode part 300 may be further
formed inside the substrate elevator 320.

[0044] The electrostatic chuck 340 is provided on the substrate elevator
320. The electrostatic chuck 340 may be formed in a shape that is similar
to the shape of the substrate G that may be mounted on the upper surface
of the electrostatic chuck 340. The electrostatic chuck 340 attaches and
fixes the substrate G loaded inside the reaction chamber 100. That is,
the electrostatic chuck 340 is connected to the high voltage DC power
source 800, thereby attaching and maintaining the substrate G by the
electrostatic force formed by the high voltage DC power source 800. The
substrate is attached to and held in place by the electrostatic force of
the electrostatic chuck 340. However, using electrostatic force to hold
the substrate in place is not a limitation of the invention and a
mechanical chuck using vacuum force or mechanical force may be used.

[0045] A focusing ring 380 may be further provided according to the
external circumferential surface of the substrate G loaded on the
electrostatic chuck 340. The focusing ring 380 is formed according to the
external circumferential surface of the substrate G, thereby
concentrating the reaction gas of the plasma state formed inside the
reaction chamber 100 to the substrate G.

[0046] Meanwhile, the baffle plate 400 is installed around and in contact
with the external circumferential surface of the electrostatic chuck 340.
The baffle plate 400 uniformly moves the reaction gas supplied inside the
reaction chamber 100 downward such that the flow of the reaction gas
around the substrate G mounted to the electrostatic chuck 340 is
constantly maintained. By maintaining the concentration of reaction gas
around the substrate G substantially constant, the baffle plate 400 helps
achieve uniform etching on the substrate G.

[0047] Referring to FIG. 2, the baffle plate 400 has an approximately
quadrangular planer shape. The baffle plate 400 includes an opening (not
shown) into which the electro-static chuck 340 is inserted. The external
circumferential surface of the baffle plate 400 is approximately the same
size as the inner wall of the reaction chamber 400, and the interior
circumference (i.e., the size of the opening) is approximately the same
size as that of the external circumferential surface of the electrostatic
chuck 340.

[0048] A plurality of cutouts 410 through which the gas passes are formed
in the baffle plate 400 such that the reaction gas inside the reaction
chamber 100 is uniformly moved under the baffle plate 400 and out of the
reaction chamber 100.

[0049] The cutouts 410, which may have a semi-circular cross section, are
formed along the edges of the baffle plate 400, in the form of a recess
portion at the edges of the baffle plate 400. The diameter of each cutout
410 may be about 1/18 times to 1/23 times of the long axis (X-axis)
length of the baffle plate 400. For example, if the long axis length of
the baffle plate is 2740 mm, the diameter of the cutout 410 may be 134
mm.

[0050] The cutout 410 is positioned close to the corner C of the baffle
plate 400 from a position bisecting each edge of the baffle plate 400.
That is, a distance L1 is preferably 1.3 times to 1.9 times the diameter
of the cutout 410, wherein the distance L1 is measured from an imaginary
extension of an edge of the focusing ring 380 to the nearest point of the
cutout 410.

[0051] Table 1 shows experimental data on etching uniformity for an area
of all the corners of a baffle plate and an area of all the cutouts
according to an exemplary embodiment of the present invention.

[0052] Referring to Table 1, in the baffle plate 400, it may be confirmed
that as the ratio of the corner area: the cutout area changes to 100:25,
100:20, 100:19, and 100:18, the uniformity is increased.

[0053] Accordingly, it is preferable that the ratio of the corner area:
cutout area is larger than 100:0 and less than 100:18.

[0054] In the exemplary embodiment of the present invention, the cutouts
410 are formed with constant diameter. However, cutouts having different
diameters may be formed when considering the ratio of the baffle plate
area and the cutout area.

[0055] Accordingly, in the exemplary embodiment of the present invention,
the cutouts are formed to have a semicircular cross section, however they
may be formed to have a quadrangular or oval cross section when
considering the area ratio.

[0056] Also, as shown in FIG. 3, each cutout 410 includes a plurality of
slits 41, and the interval L3 between the slits 41 is less than the width
of the above-described cutouts 410. Though the diameter of the cutouts
410 is larger than the above-described value (that is, 1/23 times of the
long axis (X-axis) length of the baffle plate), if a plurality of slits
41 are formed, since the diameter of the cutouts 410 is decreased by
parts between the slits 41, the etching may be uniformly executed.

[0057] The gas inserted inside the chamber flows under the substrate
through a pumping port positioned at the corner of the baffle plate, and
is then discharged through the exhaust port 120. Due to the gas flow, the
portion of the substrate positioned near the pumping port may be
over-etched when etching the substrate. The pumping port as a portion
enclosed by an extension line (a dotted line) of the focusing ring in
FIG. 2 is positioned at the corner of the baffle plate.

[0058] However, as shown in an exemplary embodiment of the present
invention, if the baffle plate including a cutout positioned near the
pumping port is installed, the flow pattern of fluid in the reaction
chamber is changed such that over-etching of the substrate near the
pumping port may be prevented. Accordingly, the entire substrate may be
uniformly etched. As shown in FIG. 4 and FIG. 5, when measuring the
surface stress, the averages of the surface stresses of a conventional
art and the present invention are found to be the same. However, it may
be confirmed that the distribution range of the surface stress according
to the present invention is narrower than the conventional art. That is,
the changing width of the surface stress is decreased by the baffle plate
according to the present invention such that uniform etching may be
executed for the entire substrate.

[0059] While this invention has been described in connection with what is
presently considered to be practical exemplary embodiments, it is to be
understood that the invention is not limited to the disclosed
embodiments, but, on the contrary, is intended to cover various
modifications and equivalent arrangements included within the spirit and
scope of the appended claims.